EP3173845A1 - Optical scanning apparatus and image forming apparatus including the same - Google Patents

Optical scanning apparatus and image forming apparatus including the same Download PDF

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Publication number
EP3173845A1
EP3173845A1 EP16200358.6A EP16200358A EP3173845A1 EP 3173845 A1 EP3173845 A1 EP 3173845A1 EP 16200358 A EP16200358 A EP 16200358A EP 3173845 A1 EP3173845 A1 EP 3173845A1
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EP
European Patent Office
Prior art keywords
optical system
scanning
scanning apparatus
optical scanning
scanned
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16200358.6A
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German (de)
English (en)
French (fr)
Inventor
Noa Sumida
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Canon Inc
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Canon Inc
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Publication date
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP3173845A1 publication Critical patent/EP3173845A1/en
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/101—Scanning systems with both horizontal and vertical deflecting means, e.g. raster or XY scanners
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/04—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/04—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
    • G03G15/043—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material with means for controlling illumination or exposure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/106—Scanning systems having diffraction gratings as scanning elements, e.g. holographic scanners
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/12—Scanning systems using multifaceted mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/12—Scanning systems using multifaceted mirrors
    • G02B26/125—Details of the optical system between the polygonal mirror and the image plane
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0275—Arrangements for controlling the area of the photoconductor to be charged
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/00795—Reading arrangements
    • H04N1/00798—Circuits or arrangements for the control thereof, e.g. using a programmed control device or according to a measured quantity
    • H04N1/00816—Determining the reading area, e.g. eliminating reading of margins
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/024—Details of scanning heads ; Means for illuminating the original
    • H04N1/028—Details of scanning heads ; Means for illuminating the original for picture information pick-up
    • H04N1/02815—Means for illuminating the original, not specific to a particular type of pick-up head
    • H04N1/0282—Using a single or a few point light sources, e.g. a laser diode
    • H04N1/0283—Using a single or a few point light sources, e.g. a laser diode in combination with a light deflecting element, e.g. a rotating mirror
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/23—Reproducing arrangements
    • H04N1/29—Reproducing arrangements involving production of an electrostatic intermediate picture

Definitions

  • the present invention relates to an optical scanning apparatus, and to an optical scanning apparatus effectively usable together with an image forming apparatus, such as a laser beam printer (LBP), a digital copying machine, and a multifunction printer (a printer equipped with multiple functions).
  • an image forming apparatus such as a laser beam printer (LBP), a digital copying machine, and a multifunction printer (a printer equipped with multiple functions).
  • an optical scanning apparatus including an incident optical system, which guides a light flux emitted from a light source to a deflector, and an imaging optical system, which guides the light flux deflected by the deflector to a surface to be scanned, as an optical scanning apparatus for use in an image forming apparatus.
  • Japanese Patent Application Laid-Open No. 2015-31824 discusses an optical scanning apparatus configured in such a manner that the imaging optical system is disposed closer to the deflector, which contributes to reductions in a length of the imaging optical system in a main-scanning direction and a length of the entire apparatus in an optical-axis direction, thus realizing reductions in a size and cost.
  • the image forming apparatus requires an area for placing other members, such as a toner container, whereby it is difficult to reduce a distance between the imaging optical system and the surface to be scanned. Therefore, reducing the distance between the deflector and the imaging optical system, like the configuration discussed in Japanese Patent Application Laid-Open No. 2015-31824 , leads to a necessity of increasing a lateral magnification of the imaging optical system in a sub-scanning cross-section (a sub-scanning magnification). Therefore, this configuration ends up increasing a sensitivity of the optical performance to a variation in the imaging optical system at the time of the formation thereof. That is, the configuration increases the amount of a change in optical performance according to a variation in the imaging optical system at the time of manufacture, and an assembly error in each member such as the light source.
  • one possible method for solving this problem is to reduce a sub-scanning magnification of the incident optical system to thereby reduce a sub-scanning magnification of the entire optical system, thus preventing or reducing the increase in the sensitivity of the optical performance.
  • simply increasing a distance between the light source and the incident optical system to achieve that leads to a necessity of enlarging the incident optical system in the sub-scanning direction, making it difficult to reduce a size of the incident optical system.
  • the present invention is directed to realizing the reduction in the size while reducing the sensitivity of the optical performance in the optical scanning apparatus.
  • the present invention in its first aspect provides an optical scanning apparatus as specified in claims 1 to 9.
  • a main-scanning direction refers to a direction perpendicular to a rotational axis (or an axis of a swinging motion) of a deflector and perpendicular to an optical-axis direction of an imaging optical system.
  • the main-scanning direction is a direction in which a surface to be scanned is optically scanned by the deflector.
  • a sub-scanning direction refers to a direction in parallel with the rotational axis or the axis of the swinging motion of the deflector.
  • a main-scanning cross-section refers to a cross-section including an optical axis and parallel with the main-scanning direction, i.e., a cross-section perpendicular to the sub-scanning direction.
  • a sub-scanning cross-section refers to a cross-section in parallel with the optical axis of the imaging optical system and the sub-scanning direction, i.e., a cross-section perpendicular to the main-scanning direction.
  • Figs. 1A and 1B are cross-sectional views illustrating main portions of an optical scanning apparatus 10 according to a first exemplary embodiment of the present invention.
  • Figs. 1A and 1B illustrate a view of the main-scanning cross-section (an XY cross-sectional view), and a view of the sub-scanning cross-section (a ZX cross-sectional view) including the optical axis of the imaging optical system, respectively.
  • the optical scanning apparatus 10 includes a light source 1, an incident optical system 2, an aperture stop 3, a deflector 4, and an imaging optical system 5, and is an apparatus that optically scans a surface to be scanned 6 by deflecting a light flux with use of the deflector 4.
  • the optical scanning apparatus 10 may employ such a configuration that a deflecting mirror (a reflection member) is disposed in an optical path from the deflection surface 4a to the surface to be scanned 6, by which the optical path is deflected in the sub-scanning cross-section.
  • a deflecting mirror a reflection member
  • the light flux emitted from the light source 1, after passing through the incident optical system 2, is formed into an elliptical shape by the aperture stop 3 including an elliptical aperture, and is incident on the deflection surface 4a of the deflector 4.
  • a semiconductor laser can be used as the light source 1, and the number of light emitting points thereof may be one or plural.
  • the elliptical aperture stop including the elliptical aperture is employed as the aperture stop 3, but the shape of the aperture is not limited thereto.
  • a rectangular aperture stop including a rectangular aperture may be employed as the aperture stop 3.
  • the incident optical system 2 is an anamorphic collimator lens having positive refracting power in the main scanning cross-section, and converts the light flux into substantially parallel light in the main scanning cross-section.
  • the substantially parallel light here includes not only precisely parallel light but also weakly convergent light and weakly divergent light. Then, the incident optical system 2 condenses the light flux on or around the deflection surface 4a in the sub-scanning cross-section to form a line image elongated in the main-scanning direction on the deflection surface 4a.
  • the deflector 4 is rotated by a driving unit (not illustrated) at a constant speed in a direction from the incident optical system 2 to the imaging optical system 5 in the main-scanning cross-section, as indicated by an arrow illustrated in the drawing.
  • the deflector 4 deflects the light flux from the aperture stop 3 by the deflection surface 4a to optically scan an effective scanning area (a printing area) on the surface to be scanned 6 in the main-scanning direction via the imaging optical system 5.
  • a rotational polygonal mirror (a polygon mirror) having four deflection surfaces is employed as the deflector 4, but the number of deflection surfaces is not limited thereto.
  • a swingable mirror having one or two deflection surface(s) swingable around an axis of a swinging motion may be employed instead of the rotational polygonal mirror.
  • the imaging optical system 5 includes a single imaging optical element (an imaging lens), and guides and condenses the light flux deflected by the deflection surface 4a onto the surface to be scanned 6 to form an image of the light source 1 on or around the surface to be scanned 6 in both the main-scanning cross-section and the sub-scanning cross-section.
  • the imaging optical system 5 has two optical surfaces (lens surfaces), namely, an incident surface (a first surface) 5a and an emission surface (a second surface) 5b.
  • the imaging optical system 5 is configured to allow the surface to be scanned 6 to be scanned at an even speed with the light flux deflected by the deflection surface 4a, i.e., to satisfy the f ⁇ characteristic in the main-scanning cross-section.
  • the imaging optical system 5 establishes a conjugate relationship between the deflection surface 4a or the vicinity thereof and the surface to be scanned 6 or the vicinity thereof in the sub-scanning cross-section, thereby reducing a shift of a scanning position on the surface to be scanned 6 in the sub-scanning direction when the deflection surface 4a tilts (optical face tangle error compensation).
  • each of the incident optical system 2 and the imaging optical system 5 includes a single optical element, but each of them may include a plurality of optical elements if necessary.
  • the incident optical system 2 may include two optical elements, a collimator lens and an anamorphic lens.
  • each of the incident optical system 2 and the imaging optical system 5 is a plastic molded lens formed by injection molding, but is not limited thereto and may be a glass lens. Further, in the case where each of the incident optical system 2 and the imaging optical system 5 includes the plurality of optical elements, they may be constructed by combining the glass lens and the plastic molded lens. However, it is desirable to employ the plastic molded lens, which makes it easy to form a diffractive surface and an aspherical shape and is suited for mass-production, to improve productivity and an optical performance.
  • a configuration of the optical scanning apparatus 10 according to the present exemplary embodiment is indicated in a table 1.
  • An on-axis deflection point in the table 1 refers to a point at which, when the light flux from the light source 1 is incident on a position of an on-axis image height of the surface to be scanned 6, a principal ray of this light flux and the deflection surface 4a intersect with each other.
  • a shape x of each of the optical surfaces of the imaging optical system 5 is defined by the following expressions (1) to (4), when an origin, an X axis, a Y axis, and a Z axis are set to an intersection point between the optical surface and the optical axis, the X axis extending in the optical-axis direction, the Y axis orthogonal to the optical axis in the main-scanning cross-section, and the Z axis orthogonal to the optical axis in the sub-scanning cross-section, respectively.
  • the expression (2) indicates a shape of the optical surface in the main-scanning cross-section (a generatrix shape), and the expression (3) indicates a shape of the optical surface in the sub-scanning cross-section (a sagittal shape) at a position of an image height Y.
  • a curvature radius r' of the optical surface in the sub-scanning cross-section changes according to a value of Y.
  • each aspheric surface coefficient is set assuming that Y corresponds to "upper” in the case of Y > 0 and "lower” in the case of Y ⁇ 0.
  • ⁇ 2 ⁇ ⁇ k ⁇ i , j c i , j Y i Z j
  • the plastic molded lens is employed as the incident optical system 2 and the optical surface thereof is formed as the diffractive surface, which allows the incident optical system 2 to compensate the focus change due to the change in the ambient temperature.
  • the power the refracting power
  • the diffractive surface is enhanced due to the elongated wavelength of the light flux, which allows the focus changes due to the refractive surface and the diffractive surface to cancel out each other.
  • FIGs. 2A and 2B are cross-sectional views illustrating main portions of an optical scanning apparatus 20 according to the comparative example, and Fig. 2A and 2B illustrate a view of a main-scanning cross-section, and a view of a sub-scanning cross-section including the optical axis of the imaging optical system 5, respectively.
  • a configuration of the optical scanning apparatus 20 according to the comparative example is illustrated in a table 2.
  • the shape x of each of the optical surfaces of the imaging optical system 5 according to the comparative example is expressed by the above-described expressions (1) to (3) and the following expression (6).
  • the distance between the deflector 4 and the imaging optical system 5 can be shorter and the width of the imaging optical system 5 in the main-scanning direction can be narrower in the present exemplary embodiment than the comparative example.
  • of the sub-scanning magnification of the imaging optical system 5 is larger in the present exemplary embodiment than the comparative example as this value is 3.42 times in the present exemplary embodiment while being 2.40 times in the comparative example.
  • of the sub-scanning magnification of the incident optical system 2 can reduce the absolute value
  • of the sub-scanning magnification of the incident optical system 2 leads to a necessity of enlarging the incident optical system 2 in the sub-scanning direction.
  • FIG. 3A is a schematic drawing illustrating a sub-scanning cross-section when the entire optical system according to the comparative example is developed so as to be lined up on the same axis
  • configurations in Figs. 3B and 3C are configurations in which the distance between the deflection surface 4a and the imaging optical system 5 is reduced from the configuration in the first row, respectively.
  • a configuration in Fig. 3D is a schematic diagram illustrating a sub-scanning cross-section when the entire optical system according to the present exemplary embodiment is developed so as to be lined up on the same axis.
  • the configuration in Fig. 3B compared to the configuration in Fig. 3A , places the light source 1 farther away from the incident optical system 2 while maintaining an f-number (Fno) of the imaging optical system 5 on a scanning side that faces the surface to be scanned 6, thereby reducing the absolute value
  • the configuration in Fig. 3C compared to the configuration in Fig. 3A , places the incident optical system 2 closer to the deflection surface 4a, thereby reducing the absolute value
  • are
  • 2 in the configuration in Fig. 3A , and then the distance between the deflection surface 4a and the imaging optical system 5 is changed from this configuration, so that the absolute value
  • 3.
  • should be changed to
  • 1.33 to keep the absolute value
  • the optical scanning apparatus 10 satisfies the following conditional expressions (7) to (9), when Li represents the distance between the light source 1 and the deflection surface 4a on the optical axis, i.e., the distance between the light emitting point of the light source 1 and the on-axis deflection point. 0.5 ⁇ ⁇ si ⁇ 2.2 3.0 ⁇ ⁇ so ⁇ 10.0 0.2 ⁇ Li / Lo ⁇ 0.4
  • the conditional expression (7) indicates that the sub-scanning magnification of the incident optical system 2 is small to some degree, i.e., the incident optical system 2 is disposed at a position that is close to the deflection surface 4a to some degree.
  • the conditional expression (8) indicates that the sub-scanning magnification of the imaging optical system 5 is large to some degree, i.e., the imaging optical system 5 is disposed at a position that is close to the deflection surface 4a to some degree.
  • the conditional expression (9) indicates that the light source 1 is disposed at a position that is close to the deflection surface 4a to some degree.
  • the sub-scanning magnification of the incident optical system 2 falls below a lower limit defined by the conditional expression (7), the incident optical system 2 is disposed too close to the deflection surface 4a, which makes it difficult to manufacture the optical scanning apparatus 10. If the sub-scanning magnification of the incident optical system 2 exceeds an upper limit defined by the conditional expression (7), the sub-scanning magnification of the incident optical system 2 becomes too large, which makes it difficult to reduce the sensitivity of the optical performance.
  • the imaging optical system 5 is disposed too far away from the deflection surface 4a, which makes it difficult to reduce the size of the entire apparatus in the optical-axis direction. If the sub-scanning magnification of the imaging optical system 5 exceeds an upper limit defined by the conditional expression (8), the imaging optical system 5 is disposed too close to the deflection surface 4a, which makes it difficult to manufacture the optical scanning apparatus 10.
  • the light source 1 is disposed too close to the incident optical system 2, which makes it difficult to manufacture the optical scanning apparatus 10. Further, if the relationship between the distances Li and Lo exceeds an upper limit defined by the conditional expression (9), the light source 1 is disposed too far away from the incident optical system 2, which makes it difficult to prevent or reduce the enlargement of the incident optical system 2 in the sub-scanning direction.
  • the optical scanning apparatus 10 can achieve both the reduction in the size of the imaging optical system 5 and the prevention or reduction in the enlargement of the incident optical system 2 while reducing the sub-scanning magnification of the entire optical system, thereby realizing the reduction in the size of the entire apparatus.
  • This effect allows the optical scanning apparatus 10 to reduce material cost (achieve cost-cutting) regarding each of the optical systems while reducing the sensitivity of the optical performance of the entire optical system.
  • both the light source 1 and the incident optical system 2 are disposed closer to the deflection surface 4a compared to the configuration in Fig. 3A , unlike the configurations in Figs. 3B and 3C . Due to this layout, the configuration in Fig. 3D succeeds in preventing or reducing the enlargement of the incident optical system 2 in the sub-scanning direction while reducing the distance of each of the incident optical system 2 and the imaging optical system 5 to the deflection surface 4a.
  • a light flux width Hd on the emission surface of the incident optical system 2 according to the present exemplary embodiment is 2.55 mm, and is significantly narrower compared to Hb and Hc in the configurations in Figs. 3B and 3C .
  • the incident optical system 2 satisfies the following conditional expression (10). 1.0 ⁇ ⁇ si ⁇ 1.9
  • is
  • 1.76, and satisfies both the above-described conditional expressions (7) and (10). Therefore, ⁇ s can reduce to as small as 6.02, which is substantially equal to the comparative example. If the incident optical system 2 according to the present exemplary embodiment is replaced with the incident optical system according to the comparative example, the absolute value
  • 8.21, resulting in an increase in the sensitivity of the optical performance to the assembly precision of each of the members. Similarly, it is further desirable that the imaging optical system 5 satisfies the following conditional expression (11) if taking into consideration the heat generation due to the rotation of the deflector 4 and the assembly tolerance of each of the members. 3.0 ⁇ ⁇ so ⁇ 6.0
  • the optical scanning apparatus 10 satisfies the following conditional expression (12), when A represents the width of the effective scanning area (the effective scanning width) in the main-scanning direction that is targeted for the optical scanning on the surface to be scanned 6. 0.38 ⁇ Lo / A ⁇ 0.75
  • the reduction in the size can be realized while the sensitivity of the optical performance is reduced.
  • FIGS. 4A and 4B are cross-sectional views illustrating main portions of an optical scanning apparatus 40 according to the present exemplary embodiment, and Fig. 4A and 4B illustrate a main-scanning cross section and a sub-scanning cross section, respectively.
  • a configuration of the optical scanning apparatus 40 according to the present exemplary embodiment is indicated in a table 3.
  • each of the optical surfaces of the imaging optical system 5 according to the present exemplary embodiment is also expressed by the definitional expressions indicated by the expressions (1) to (4), similarly to the first exemplary embodiment.
  • the imaging optical system 5 according to the present exemplary embodiment is configured to cause the surface to be scanned 6 to be scanned at an uneven speed with the light flux deflected by the deflection surface 4a, i.e., dissatisfy the f ⁇ characteristic in the main-scanning cross-section.
  • the optical surfaces should be formed into largely different shapes between an on-axis image height and an off-axis image height in the main-scanning cross-section to allow the imaging optical system 5 to have the f ⁇ characteristic, like the first exemplary embodiment. Then, placing the imaging optical system 5 too close to the deflector 4 leads to a sharp change in the shape of the optical surface in the main-scanning cross-section, resulting in an increase in comatic aberration. Therefore, the imaging optical system 5 should be disposed a certain distance away from the deflector 4 to maintain both the optical performance and the f ⁇ characteristic of the imaging optical system 5.
  • the imaging optical system 5 is configured to have such a scanning characteristic that the light flux does not satisfy the evenness of the speed on the surface to be scanned 6, which allows the imaging optical system 5 to be disposed further close to the deflector 4 while maintaining the optical performance, thereby realizing a further reduction in the size of the entire apparatus.
  • the scanning characteristic of the imaging optical system 5 is expressed by the following expression (14), when ⁇ represents a scanning angle (a scanning field angle) by the deflector 4, Y [mm] represents a light condensing position (an image height) of the light flux deflected with the scanning angle ⁇ on the surface to be scanned 6 in the main-canning direction, and f [mm] represents an imaging coefficient at the on-axis image height.
  • Y f ⁇ ⁇ + ⁇ ⁇ ⁇ 3
  • the imaging coefficient f is a coefficient for establishing a proportional relationship between the light condensing position Y and the scanning angle ⁇ when light fluxes having all kinds of convergence including the parallel light flux are incident on the imaging optical system 5.
  • the expression (14) corresponds to such a scanning characteristic that the proportional relationship is not established between the light condensing position Y and the scanning angle ⁇ .
  • the expression that expresses the scanning characteristic of the imaging optical system 5 is not limited to the above-described expression (14).
  • the expression (16) indicates a deviation amount of the evenness of the speed at each off-axis image height from the evenness of the speed at the on-axis image height, i.e., a deviation amount of a partial magnification (a deviation of a partial magnification) at the off-axis image height from a partial magnification at the on-axis image height.
  • the optical scanning apparatus 40 according to the present exemplary embodiment has a partial magnification, so that ⁇ ⁇ 0 means that the scanning speed of the light flux is different between at the on-axis image height and at the off-axis image height.
  • the scanning position (a scanning distance per unit time) at the off-axis image height is stretched according to the deviation of the partial magnification, whereby optically scanning the surface to be scanned 6 without taking into consideration this deviation of the partial magnification leads to deterioration of the image formed on the surface to be scanned 6 (deterioration of the printing performance).
  • a modulation timing (a light emission timing) and a modulation duration (a light emission duration) of the light source 1 are controlled by a control unit (not illustrated) according to the deviation of the partial magnification if the coefficient ⁇ is ⁇ ⁇ 0.
  • This control allows the optical scanning apparatus 40 to electrically correct the scanning position and the scanning time on the surface to be scanned 6, thereby allowing the optical scanning apparatus 40 to correct the deviation of the partial magnification and thus the deterioration of the image, acquiring a printing performance as excellent as that obtained when the f ⁇ characteristic is satisfied.
  • the distance between the imaging optical system 5 and the deflection surface 4a can be shorter, and the width of the imaging optical system 5 in the main-scanning direction can also be considerably narrower compared with the first exemplary embodiment and the comparative example.
  • the sub-scanning magnification of the incident optical system 2 and the layout of each of the members are also appropriately set so as to satisfy the above-described conditional expressions (7) to (9), thereby allowing the optical scanning apparatus 40 to achieve both the reduction in the sub-scanning magnification of the entire optical system and the reduction in the size of the entire apparatus.
  • of the incident optical system 2 is 1.56 times, and the sub-scanning magnification
  • the value of Li/Lo is 0.33 and the light flux width on the emission surface of the incident optical system 2 is 2.01 mm in the present exemplary embodiment, whereby the reduction in Li and the reduction in the light flux width can be realized compared to the comparative example.
  • Fig. 5 is a schematic diagram (a view of a sub-scanning cross-section) illustrating main portions of an image forming apparatus 104 according to an exemplary embodiment of the present invention.
  • the image forming apparatus 104 includes an optical scanning unit 100, which is the optical scanning apparatus according to any of the above-described individual exemplary embodiments.
  • This code data Dc is converted into image data (dot data) Di by a printer controller 111 in the apparatus, and is input to the optical scanning unit 100.
  • a light flux 103 modulated according to the image signal Di is emitted from this optical scanning unit 100, and a photosensitive surface (a surface to be scanned) of a photosensitive drum 101 is scanned with this light flux 103 in the main-scanning direction.
  • the printer controller 111 is in charge of not only the above-described conversion of the data but also control of each unit in the image forming apparatus 104, such as a motor 105, which will be described below.
  • the photosensitive drum 101 serving as an electrostatic latent image bearing member (a photosensitive member) is rotated by the motor 105 in a clockwise direction. Then, the photosensitive surface of the photosensitive drum 101 is displaced relative to the light flux 103 in the sub-scanning direction according to this rotation.
  • a charging roller 102 which evenly charges the photosensitive surface, is disposed above the photosensitive drum 101 in abutment with the photosensitive surface. Then, the image forming apparatus 104 is configured in such a manner that the photosensitive surface charged by the charging roller 102 is irradiated with the light flux 103 from the optical scanning unit 100.
  • the light flux 103 is modulated based on the image signal Di, and the irradiation with this light flux 103 causes an electrostatic latent image to be formed on the photosensitive surface.
  • This electrostatic latent image is developed as a toner image by a developing unit 107, which is disposed in abutment with the photosensitive surface on a further downstream side of the position irradiated with the light flux 103 in the rotational direction of the photosensitive drum 101.
  • the toner image developed by the developing unit 107 is transferred onto a sheet 112 serving as a transfer material by a transfer roller (a transfer unit) 108 disposed opposite from the photosensitive drum 101 below the photosensitive drum 101.
  • the sheet 112 is contained in a sheet cassette 109 located in front of the photosensitive drum 101 (a right side in Fig. 5 ), but can also be fed manually.
  • a sheet feeding roller 110 is disposed at an end of the sheet cassette 109, by which the sheet 112 in the sheet cassette 109 is fed onto a conveyance path.
  • the sheet 112 with the unfixed toner image transferred thereon is further conveyed to a fixing unit disposed behind the photosensitive drum 101 (a left side in Fig. 5 ).
  • the fixing unit includes a fixing roller 113, which has a fixing heater (not illustrated) therein, and a pressing roller 114, which is disposed in pressure contact with this fixing roller 113.
  • This fixing unit fixes the unfixed toner image on the sheet 112 by heating the sheet 112 conveyed from the transfer roller 108 while pressing this sheet 112 at a pressure contact portion between the fixing roller 113 and the pressing roller 114.
  • a sheet discharge roller 116 is disposed behind the fixing roller 113, and the sheet 112 with the toner image fixed thereon is discharged outward from the image forming apparatus 104.
  • the image forming apparatus 104 may be configured as a color image forming apparatus by being provided with a plurality of units as each of the optical scanning unit 100, the photosensitive drum 101, and the developing unit 107. Further, a color digital copying machine may be constructed by connecting a color image reading apparatus including a line sensor, such as a charge coupled device (CCD) sensor and a complementary metal-oxide semiconductor (CMOS) sensor, to the image forming apparatus 104 as the external apparatus 117.
  • a line sensor such as a charge coupled device (CCD) sensor and a complementary metal-oxide semiconductor (CMOS) sensor
  • the present invention is not limited to these exemplary embodiments and examples, and these exemplary embodiments and examples can be combined, modified, and changed in various manners within the range of the spirit of the present invention.
  • each of the above-described exemplary embodiments employs the configuration that optically scans the single surface to be scanned 6 with the light flux from the single light source 1, but the present invention is not limited thereto and may employ a configuration that simultaneously deflects light fluxes from a plurality of light sources by a single deflector to optically scan a plurality of surface to be scanned.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Plasma & Fusion (AREA)
  • Facsimile Scanning Arrangements (AREA)
  • Laser Beam Printer (AREA)
  • Mechanical Optical Scanning Systems (AREA)
  • Lenses (AREA)
EP16200358.6A 2015-11-26 2016-11-23 Optical scanning apparatus and image forming apparatus including the same Withdrawn EP3173845A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2015231167A JP6230586B2 (ja) 2015-11-26 2015-11-26 光走査装置及びそれを備える画像形成装置

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EP3173845A1 true EP3173845A1 (en) 2017-05-31

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US (1) US9874831B2 (enrdf_load_stackoverflow)
EP (1) EP3173845A1 (enrdf_load_stackoverflow)
JP (1) JP6230586B2 (enrdf_load_stackoverflow)
KR (1) KR102035380B1 (enrdf_load_stackoverflow)
CN (1) CN106896669B (enrdf_load_stackoverflow)

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JP6425752B2 (ja) * 2017-03-09 2018-11-21 キヤノン株式会社 光走査装置及びそれを備える画像形成装置
JP6657344B1 (ja) * 2018-08-27 2020-03-04 哲理 園田 情報伝達システム
CN109491077B (zh) 2018-12-29 2020-11-17 珠海奔图电子有限公司 光学扫描设备和电子成像装置
JP7417425B2 (ja) * 2020-01-15 2024-01-18 キヤノン株式会社 光走査装置及び画像形成装置

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CN106896669B (zh) 2019-11-15
KR102035380B1 (ko) 2019-10-22
JP6230586B2 (ja) 2017-11-15
KR20170061614A (ko) 2017-06-05
US20170153565A1 (en) 2017-06-01
JP2017097244A (ja) 2017-06-01
US9874831B2 (en) 2018-01-23
CN106896669A (zh) 2017-06-27

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